1. Field of the Invention
This invention generally relates to an apparatus for controlling an engine such as an automotive engine. This invention particularly relates to an apparatus for automatically stopping and restarting an automotive engine.
2. Description of the Related Art
Japanese patent application publication number 58-166165 discloses a vehicle powered by an internal combustion engine and having an automatic transmission. The automatic transmission is provided with a torque converter and a lock-up clutch. The lock-up clutch selectively couples and uncouples the input shaft and the output shaft of the torque converter to and from each other. In Japanese application 58-166165, when an engine throttle valve is fully closed and the vehicle speed and the engine speed are higher than prescribed speeds, the supply of fuel to the engine is cut off. During the execution of the fuel cut-off, a decision is made as to whether or not the rate of the drop in the vehicle speed is higher than a prescribed value. When the vehicle-speed drop rate is higher than the prescribed value, the lock-up clutch is set in a disengaged position at which the input shaft and the output shaft of the torque converter are uncoupled from each other. On the other hand, when the vehicle-speed drop rate is lower than the prescribed value, the lock-up clutch is set in an engaged position at which the input shaft and the output shaft of the torque converter are coupled to each other.
Japanese patent application publication number 11-257115 discloses an engine stop control apparatus for a vehicle equipped with an automatic transmission. In the apparatus of Japanese application 11-257115, the supply of fuel to an engine is cut off and then the fuel supply is resumed under prescribed vehicle operating conditions. During deceleration of the vehicle, resumption of the fuel supply is inhibited when the automatic-transmission shift position is an N position or a P position, or when a brake pedal is depressed although the shift position is a D position or an R position. The inhibition of resumption of the fuel supply prevents the engine from unnecessarily idling. In the apparatus of Japanese application 11-257115, even when the brake pedal is lightly depressed and then an accelerator pedal is depressed, the engine is stopped and subsequently restarted. The engine stop and subsequent engine restart cause a rough ride in the vehicle.
Japanese patent application publication number 8-189395 discloses an apparatus for automatically starting and stopping an automotive engine. The features of the apparatus of Japanese application 8-189395 are as follows. Even in conditions for the cutoff of fuel supply to the engine are not satisfied, the fuel cut-off is executed provided that conditions for automatic engine stop are satisfied. During the satisfaction of the conditions for automatic engine stop, when clutch releasing conditions are satisfied, a clutch is controlled in its release state and the engine is automatically stopped. When conditions for automatic engine start are satisfied, the engine is controlled to automatically start. When conditions for normal clutch control are satisfied, the clutch is controlled in its normal state.
Japanese patent application publication number 2-200538 discloses an apparatus for controlling a vehicle powered by an engine and including an automatic transmission and a motor/generator. The automatic transmission has a torque converter provided with a lock-up clutch. Operation of the motor/generator can be changed between a motor mode and a generator mode. During the motor mode of operation, the motor/generator operates as a motor for driving the engine. During the generator mode of operation, the motor/generator operates as a generator driven by the engine. The supply of fuel to the engine can be selectively cut off and resumed. During a fuel supply resuming procedure, the lock-up clutch is set in a disengaged state, and then the engine is driven by the motor/generator. Thus, the setting of the lock-up clutch in its disengaged state is always followed by the drive of the engine by the motor/generator. Since the drive of the engine by the motor/generator consumes power, the setting of the lock-up clutch in its disengaged state is always followed by a power consumption stage.
It is an object of this invention to provide an engine control apparatus which gives a better ride in a vehicle.
A first aspect of this invention provides an engine control apparatus comprising brake depression degree detecting means for detecting a degree of depression of a brake pedal in a vehicle; brake depression degree judging means for judging whether or not the detected degree of depression of the brake pedal is smaller than a first prescribed value; deceleration detecting means for detecting a deceleration of the vehicle; and automatic engine stop and restart controlling means for automatically stopping an engine powering the vehicle when the deceleration detecting means detects a deceleration of the vehicle and the brake depression degree judging means judges that the detected degree of depression of the brake pedal is not smaller than the first prescribed value.
A second aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising fuel supply controlling means for cutting off a supply of fuel to the engine when the deceleration detecting means detects a deceleration of the vehicle, and for resuming the supply of fuel to the engine when the brake depression degree judging means judges that the detected degree of depression of the brake pedal is smaller than the first prescribed value.
A third aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising engine speed detecting means for detecting a rotational speed of the engine, and wherein the brake depression degree judging means executes judging whether or not the detected degree of depression of the brake pedal is smaller than the first prescribed value when the rotational engine speed detected by the engine speed detecting means drops to a reference value set on the basis of a maximum speed in a range of resonance between the engine and a body of the vehicle.
A fourth aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus wherein the automatic engine stop and restart controlling means comprises means for temporarily increasing a load caused by an accessory in the vehicle when automatically stopping the engine.
A fifth aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus wherein the brake depression degree judging means operates for judging whether or not the detected degree of depression of the brake pedal is greater than a second prescribed value smaller than the first prescribed value, and the automatic engine stop and restart controlling means operates for restarting the engine when the brake depression degree judges that the detected degree of depression of the brake pedal is not greater than the second prescribed value.
A sixth aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising brake depression speed detecting means for detecting a speed of depression of a brake pedal in the vehicle, and wherein the automatic engine stop and restart controlling means inhibits automatic stop of the engine when the speed detected by the brake depression speed detecting means is higher than a predetermined speed.
A seventh aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising relative speed detecting means for detecting a relative speed between the vehicle and a preceding vehicle, and wherein the automatic engine stop and restart controlling means inhibits automatic stop of the engine when the relative speed detected by the relative speed detecting means is higher than a predetermined speed.
An eighth aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising steering angle detecting means for detecting a steering angle of a steering wheel in the vehicle, and wherein the automatic engine stop and restart controlling means inhibits automatic stop of the engine when the steering angle detecting means detects a steering angle greater than a predetermined value.
A ninth aspect of this invention is based on the first aspect thereof, and provides an engine control apparatus further comprising road surface slope angle detecting means for detecting a slope angle of a road surface which the vehicle is on, and wherein the automatic engine stop and restart controlling means inhibits automatic stop of the engine when the slope angle detected by the road surface slope angle is greater than a predetermined value.
A tenth aspect of this invention provides an engine control apparatus comprising engine speed detecting means for detecting a rotational speed of an engine; torque imparting means for imparting a torque to the engine; fuel injecting means for injecting fuel into the engine; means for activating the torque imparting means to impart a torque to the engine and activating the fuel injecting means to inject fuel into the engine to restart the engine when the rotational speed detected by the engine speed detecting means is lower than a reference speed; and means for activating the fuel injecting means to inject fuel into the engine to restart the engine without activating the torque imparting means when the rotational speed detected by the engine speed detecting means is equal to or higher than the reference speed.
An eleventh aspect of this invention is based on the tenth aspect thereof, and provides an engine control apparatus further comprising means for continuously activating the torque imparting means to continuously impart a torque to the engine until the rotational speed detected by the engine speed detecting means rises to the reference speed.
A twelfth aspect of this invention is based on the tenth aspect thereof, and provides an engine control apparatus further comprising a one-way clutch provided between the torque imparting means and a crankshaft of the engine.
A thirteenth aspect of this invention is based on the tenth aspect thereof, and provides an engine control apparatus further comprising means for detecting a warm-up condition of the engine, and means for changing the reference speed in response to the detected warm-up condition.
A fourteenth aspect of this invention provides an engine control apparatus comprising an automatic transmission changeable to a specified state in which a transmission of motive power from an engine toward axles is permitted while a transmission of motive power from the axles toward the engine is cut off; automatic engine stopping and starting means for automatically stopping the engine when prescribed engine stop conditions are satisfied, and for automatically starting the engine when prescribed engine restart conditions are satisfied; and means for changing the automatic transmission to the specified state when the automatic engine stopping and starting means automatically stops the engine.
A fifteenth aspect of this invention is based on the fourteenth aspect thereof, and provides an engine control apparatus wherein the automatic transmission is changeable to a plurality of given states in which a transmission of motive power from the engine toward the axles is permitted while a transmission of motive power from the axles toward the engine is cut off, the engine brake is expected to be effected for first ones of the given states, the engine brake is not expected to be effected for second one of the given states, and the second one of the given states is used as the specified state.
A sixteenth aspect of this invention is based on the fourteenth aspect thereof, and provides an engine control apparatus wherein the prescribed engine stop conditions are determined by vehicle deceleration and a gear position of the automatic transmission that prevents engine speed from dropping to a vehicle vibration range.
A seventeenth aspect of this invention is based on the fourteenth aspect thereof, and provides an engine control apparatus further comprising means for generating a hydraulic pressure to operate the automatic transmission during a stop of the engine.
An eighteenth aspect of this invention is based on the fourteenth aspect thereof, and provides an engine control apparatus further comprising engine speed maintaining means for maintaining a rotational speed of the engine above a predetermined speed to avoid vehicle vibration during a transitional period between commencement of the change of the automatic transmission to the specified state and completion thereof.
A nineteenth aspect of this invention is based on the eighteenth aspect of this invention, and provides an engine control apparatus wherein the engine speed maintaining means comprises means for supplying fuel to the engine.
A twentieth aspect of this invention is based on the eighteenth aspect thereof, and provides an engine control apparatus wherein the engine speed maintaining means comprises an electric motor mechanically connected with a crankshaft of the engine, and means for activating the electric motor.